Even though you just graduated from school, you are really a student for the rest of your life if you are lucky. Look in your community to see what types of professional trade organizations exist like an Ad Club or a Publicity Club for example. Many of these groups offer professional development training, seminars, webinars, conferences, etc. on topics that would be helpful to you at this point in your career. There are also national organizations that put on events with prominent speakers and panels that would be great opportunities for you to grow and learn. There is a lot of information online and books on these topics as well, but I always find you learn more from first-hand experience so ask lots of questions along the way.

Sounds like a great first job, congrats & good luck!